Eight in ten Covid cases in UK show no ‘core symptoms’, research finds

New study says well-known indicators such as cough and loss of smell are a ‘poor marker of infection’

Coronavirus test
Swabs underway at a coronavirus drive-through testing station for NHS staff in Chessington
(Image credit: Dan Kitwood/Getty Images)

The majority of people with Covid-19 exhibit no “core” symptoms when they get tested, a major new study has found.

Scientists at University College London (UCL) analysed data on more than 36,000 people tested for coronavirus in the UK between April and June and found that of the 115 who tested positive, 88 (76.5%) presented no symptoms.

And a further 9.6% of people who tested positive showed none of the classic Covid symptoms – a cough, fever, or loss of taste and smell.

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In a paper published in medical journal Clinical Epidemiology, the scientists conclude that “Covid-19 symptoms are a poor marker of (Covid) infection”.

That verdict have “prompted fears that future Covid-19 outbreaks will be hard to control without more widespread testing in the community to pick up ‘silent transmission’”, says The Guardian.

The UCL team are calling for a change in testing strategy based on the findings of their study - based on data from the Office of National Statistics (ONS) Covid Symptom Study, which surveys thousands of UK households every week regardless of whether the respondents have symptoms.

“Frequent and widespread testing of all individuals, not just symptomatic cases, at least in high-risk settings or specific locations” would be key to preventing transmission, they write.

Study co-author Irene Petersen, a professor of epidemiology at UCL, “said university students are one group who should be tested regularly, and definitely before they go home for Christmas”, The Telegraph reports.

“You may have a lot of people who are out in the society and they’re not self-isolating because they didn’t know that they are positive,” she added.

However, some experts believe the research findings may be misleading, according to the Science Media Centre, an independent press office for science.

Paul Hunter, a professor in medicine at the University of East Anglia, argues that because the study only focused on the moment of testing, the results cannot accurately determine the proportion of people with Covid who become symptomatic or remain asymptomatic at some stage during their infection.

“Anyone who was previously symptomatic and had now recovered or who were currently incubating the infection and would develop symptoms within the following hours would not be included as being symptomatic in this study,” he said.

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